MK3 warning light control unit

Skoti · Dec 27, 2008

Anyone know how to wire a mk3 warning light control unit to a 850 mk2?

I have a mk3 control unit 06 6393 which has the following connections, E+, WL, AL, AL, IGN.

My commando is also fitted with a Lucas 3 phase alternator.

Any advice including wiring harness colours would be helpful. :?

L.A.B. · Dec 27, 2008

Skoti said:
Anyone know how to wire a mk3 warning light control unit to a 850 mk2?

My commando is also fitted with a Lucas 3 phase alternator.

The 850 MkIII assmilator is meant to be used with the RM23 180W single phase alternator fitted as standard to the MkIII models, so I don't know if it will work correctly off a three-phase alternator, but you could try it?

So you can try this:

E+ = Connect to Earth/Ground (Red)
AL = Connect each of the two AL terminals to a stator output wire. (Green/Yellow and White/Green)
WL = Connect to the positive side of the charge warning lamp (battery on Neg side) (White/Brown)
IGN = Ignition circuit (White).

Skoti · Dec 27, 2008

Works a treat

Thanks very much L.A.B. you saved me time and hassle trying to work out that wiring problem.

rbt11548 · Dec 27, 2008

Skoti said:
Works a treat

Thanks very much L.A.B. you saved me time and hassle trying to work out that wiring problem.

Here is a diagram of it wired to a M3
http://i411.photobucket.com/albums/pp19 ... geside.jpg
Robert

Skoti · Dec 27, 2008

Thanks for that help Robert.

I've printed your wiring diagram and shall keep it with my workshop manual for future reference. 8)

JimC · Dec 27, 2008

I don't have a Mk 3, but why are the zeners connected to the AC output of the alternator in the wiring diagram? The zeners normal function is as a DC regulator. As pictured in the diagram they will function as a half wave rectifier. If the AC output of the alternator is above the breakdown voltage of the zener it will become somewhat of a square wave rectifier as pictured in the diagram. To function as a DC regulator they need to be connected to the DC output of the regulator. I suppose it is possible to chop the AC alternator output, limiting input to the rectifier, hence limiting DC output. Maybe this is one of Lucas better ideas.

Ron L · Dec 27, 2008

Robert's diagram is consistant with the Mk3 wiring diagram in the shop manual. However, I'm not sure it is consistant with the description of the charging system. The manual states that the stator supplies AC current to the rectifier where it is converted to half-wave DC current and fed to the battery in parallel with the zener diodes to prevent overcharging, with voltage in excess of 13 volts bled off as heat in the zener.

This description implies that the zeners are connected after the rectifier. The diagram shows them connected to the AC source prior to the rectfier. I can't see how the system would work like that, but I'm not an EE. I guess I could go down to the shop and pull the seat off my Mk3 and double check, but I'm feeling lazy at the moment.

JimC · Dec 27, 2008

Ron,

I was looking at your M/C ownership list. Do I see an increase as of late? Guess I could go back to some of your earlier posts. If it is indeed an increase, good on ya'.

I'm currently at 1-1/2. The 1/2 being my Combat. Motor still laying in a bunch of Leo Goff prepared pieces. The 1 is my 91 K75 RT. BTW, how are you on suspensions of the early K bikes?

L.A.B. · Dec 28, 2008

JimC said:
Maybe this is one of Lucas better ideas.

Yes, it's a very simple system, which has the added benefit that the Zeners do not have to be a matched pair, as they would need to be if both were connected to the DC side of the rectifier.

Skoti · Dec 28, 2008

As my mk2 850 does not have all the wires in place from the original harness under the tank to wire straight to the mk3 type warning lamp control unit, I need to run a wire from the rectifier and from the ignition feed (which is a double white wire) to the warning lamp control unit.

Do I need to run a double white wire from the ignition feed or would a single 1mm wire cope with the load? :?

L.A.B. · Dec 28, 2008

Skoti said:
I need to run a wire from the rectifier and from the ignition feed (which is a double white wire) to the warning lamp control unit.

Do I need to run a double white wire from the ignition feed or would a single 1mm wire cope with the load?

I'm not sure I understand what you mean about running a wire from the rectifier (to the assimilator?) do you mean an additional AC wire?
As there are no other wires connected between the rectifier and assimilator except for the two AC wires?

I would think that the White wire to the assimilator only needs to be a normal 1mm (14/0.30) as it's only part of the electronic warning light switching circuit: http://www.nortonownersclub.org/technic ... etail.html

Skoti · Dec 28, 2008

Hi L.A.B,

yes I mean an extra AC wire from the rectifier.

My original 850 mk2 harness has the following wires for the original warning lamp control unit (under the tank),-

double red - earth +
white/brown - WL
white/green - AL

As you know the mk3 warning lamp control unit has five connections, therefor I propose running two extra wires,-

from rectifier AC, green/yellow - AL
from ignition switch, double white - IGN -

It seems to function correctly wired as above

L.A.B. · Dec 28, 2008

Skoti said:
As you know the mk3 warning lamp control unit has five connections, therefor I propose running two extra wires,-

from rectifier AC, green/yellow - AL
from ignition switch, double white - IGN -

It seems to function correctly wired as above

The White (Ign.) wire is a battery feed to the assimilator, so I don't see any need for it to be doubled up, but it won't do any harm I suppose? The assimilator is after all, just an electronic light switch.

calbigbird · Dec 28, 2008

Another similar question

I am putting a butchered MK III back together. I have done away with the regulator and zener diodes and replaced them with a Timpani regulator/rectifier. Do I still grab the two wires coming off of the alternator and continue as the diagram indicates?

L.A.B. · Dec 28, 2008

Yes, connect all wires to the assimilator as shown in rbt11548's diagram provided that it's not a Canadian model 06-6392 "lights on" (headlamp control unit) assimilator

Ron L · Dec 28, 2008

Jim C,
No, my list has remained steady for a couple years. Although there are a couple more Commandos that lurk in pieces in the shop, otherwise I'm completely out of space.

Sorry I can't help with the K-model, I've never owned one of those, but I believe the early K front ends are quite similar to the R-series airhead.

LAB,
I never realized that the zeners on a Mk3 charging system were fed with alternating current. I looked at the diagram and read the description, which (at least to me) contradicts their diagram. I had to go down to the shop today and lift the seat on my '75 and trace the wires to realize that the diagram is correct and the description in the manual seems a bit off.

calbigbird,
The mk3 assimilator has two AC legs connected to the assimilator, so rather than two connections to the key switch you need two connections to the stator, one Green/Yellow and one White/Green.

Can any of our resident electrical experts explain to me why this change was made on the half wave rectified charging system?

L.A.B. · Dec 28, 2008

Ron L said:
the diagram is correct and the description in the manual seems a bit off.

The description given in the factory manual does appear to be accurate?

Ron L said:
Can any of our resident electrical experts explain to me why this change was made on the half wave rectified charging system?

The more powerful 180W system requires two Zeners, and that half-wave arrangement would seem to be the simplest (less rectifier diodes) and easiest (no matching Zeners) way to achieve it?

L.A.B. · Dec 28, 2008

Ron L,

The only piece of information in the factory manual's description of the charging system which I can think could be misunderstood is the part where it says, quote:- "The function of the Zener diodes is to regulate the flow of D.C. current and thus prevent overcharging of the battery."

Which could possibly be interpreted by some that; the Zeners should be on the DC side of the rectifier when in fact they are on the AC side, but of course they still regulate the DC current, regardless of the fact that they do it from the AC side of the rectifier?

Ron L · Dec 28, 2008

I guess I have always been an impatient reader and the beginning of section J2 of my Mk3 workshop manual says:
"The charging system comprises an alternator with the 6 charging coils connected permanently (fitted in the primary chaincase and driven by the engine crankshaft). This supplies alternating (A.C.) current to the rectifier where it is converted to a half-wave direct (D.C.) current. The D.C. current is fed to the lead/acid battery in parallel to the Zener diodes which are mounted on the left and right support plates for the silencer and footrests, on each side of the machine."

That's what put the idea in my head that it was regulating DC current, although it was not consistant with the diagram.

MK3 warning light control unit

Skoti

L.A.B.

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Skoti

rbt11548

Skoti

JimC

Ron L

JimC

L.A.B.

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Skoti

L.A.B.

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Skoti

L.A.B.

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calbigbird

L.A.B.

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Ron L

L.A.B.

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L.A.B.

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Ron L

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